Alternating current circuit involving rectification



Jan. 24, 1950 D. C. GIRARD ALTERNATING CURRENT CIRCUIT INVOLVING RECTIFICATION Filed June 12, 19 8 Y JNVENTOR. DE/i/V C. GNP/9P0 Patented Jan. 24, 1950 AIJTERNATING CURRENT "CIRCUIT INV DLV- ING RECTIFICATION .Dean 10. .Girald,..San Leandra, v(Jalit, assignnrfliy m'esne assignments, to National Qylinder .6% Company, a corporation iofeDelaware Application June'IZ, 194-8,Se1fialNo.*3268 10 Claims. 1

:My: invention relatesfto alternatingzcurrent circuits, and more "particularly toialternatin cur- 'rent circuits in which rectification takes place isuch-as in "circuits utilizing an electric are or other gaseous discharge device. While theinvenetion 'isi'of generalutility iniSllCh circuits, it is of particular importance in connection with alter .inating current iarc'welding, *and for :purposesof illustration, will be described 'in' its application to :an "arc welding circuit commonly employed in ithe welding ofealuminum, magnesium and other "such metals or :alloys "thereof.

"In a'conventional'circuit 'for the arc welding "of such materials, acertain amount of'rectifica- "tion occurs between the'work and the electrode. The resulting direct current "component flowing through the circuit including the secondary winding or the input or supply transformer, not only causes undue heating, but tendst'o saturate the transformer "core with direct current flux which results in increasedprimary current and -aclditional heating due to resuiting'extremely low power factor.

1T0 realize a given"output at' normal'operating conditions, therefore, 'a'm-uch larger-transformer must be employed than normally wouldbe employed were itnot"forthe presence'ofthe direct tcurrent component "fiowing through the "trans- Iformer secondary winding.

Among the objects ofmyinventi'on are:

'(1) "To providea' novel and improved" alternatin g current circuit;

2) To provide a noveland improved" alternating currentcircuit wherein'rectification is'an' in 'herent characteristic;

3(3) 'To provide a novel and" improved-"arc'weld ing circuit;

i) To provide'a novel and improved alternating *current arc welding "circuit "for the welding of aluminum, magnesium and the like;

(5) To provide a novel and improvedalternating-current'are welding circuit utilizingan inert fgastorch;

6) To provide a' novel and'iim'proved -alternatingcurrent arc welding 'circuitof increasedzoperation efiiciency;

*(7) To'provide anovel and improved'alternat- :ing currentarc weldin circuit wherein inherent rectification is caused to"improve"'the 'e'fliciency of 7 the circuit.

Additional objects of my iinvention #will be brought :out in the following description of the same; taken in conjunction -with the accompanyingrdrawingwherein the figure is a circuit diagram-tor an "alternating current arc welding 'circuit embodying thef features of the present invention.

This circuit, with reference to the drawing, involves atransformer having'a primarywinding 3 and a 'secondary' winding 5 mounted "on :a core "1. The secondary winding has one *end thereof connected to a' welding electrode 9 normally "of'i'tungstenywvhile the other'end of the secondary *winding is connected to the work I' I 'whic'hiffunctions as a *second electrode. Such electrodes constitute in efiect, a device having inherent rectifying actio'n.

'In the welding of "such metals as aluminum, magnesium and the '1ike,**the tungsten electrode is supported'ina casing l3-having connection to a source of'inert gas such helium, argon, crypton-'and"the like, which is releasable about the electrode "during weldin'g to exclude any oxidizing atmosphere fromtheregion of the arc.

'fTo stimulate a maintenance of an arc during cycle reversals "of the alternating current, it is conventional to 'enn'oloy a"high *frequency potential' which isfintroduced into the circuit through IT isin one df' 'the'connectionsfrom the input transformer l *whilethe' primary I9 of thehigh' frequency" transformer is connected to'some'high frequency "oscillator "Cnot' illustratedL In "this connectionjacondenseri I across the input transformer circuit is employed to by-pass around the 'secondary' windin ofthe input transformer; such high 'frequency current as may be introduced into the circuit from the high frequency oscillator.

As thus "far 'iiescribed, the circuit'is conventional, andfrom the 'verynature or such circuit, it is noted that "any recti'iication occurring at the arc, will of necessity haveto flow throughthe secondarywinding of the input transformer, with themesultsjpreviously indicated.

' Toward fulfillmentcf"the'obj ectsiof the'present invention'aspreviouslyset fofthjl introduce into the circuit across th'e arc, a choke 23"0'f highim pedance at the frequencies of "the alternating current flowing inthe circuit, ibut "offeringlow resistancetotheiiowof'any direct current component resulting from such rectification as takes place at the arc.

While such choke might take the form of a single winding, a more compact choke may be realized by mounting a primary winding 25 of few turns and low direct current resistance, on a core 21, and coupling thereto on the same core, a secondary winding 29 of high impedance to the alternating currents in the circuit, the impedance so offered being made maximum by tuning the secondary winding with a condenser 3! to the frequency of the current from the input transformer.

The core of the choke is preferably provided with an air gap 33 to avoid probable saturation of the core by the direct current flowing through the primary winding of the choke.

In conjunction with the aforementioned choke, a resistance 35 in one of the leads between the choke and the input transformer will serve to encourage the flow of any direct current through the choke in preference to the secondary winding of the input transformer and enhance the effectiveness of the circuit toward accomplishing the desired results.

' 'The introduction in the circuit of the resistance-choke arrangement described, not only permits of the use of a supply transformer designed to smaller dimensions both as to core and wire size, but the magnitude of the direct current component becomes somewhat larger by reason of the low resistance path provided for it. This increased direct current component has been found to greatly enhance the welding results. It is believed that this may be attributable to the fact that this component is in the proper direction to clean oxide from the work surface, and by permitting a larger direct current component to flow, the period of such cleaning, per cycle of alternating current, becomes greater, thus producing better welds and with increased penetration.

Accordingly, as an inventionof general application to alternating current circuits in which rectification takes place, the invention will materially cut down heating losses, at the same time permitting of the use of smaller and lighter weight equipment. In an alternating current arc welding circuit, the invention provides the added advantage of improved welding result.

From the above description of one form of my invention, it will be apparent that the same fulfills all the objects of the invention as previously recited, and while I have discussed this particular form of my invention in considerable detail, the same is subject to alteration and modification without departing from the underlying principles involved, and I accordingly do not desire to be limited in my protection to such details, except as may be necessitated by the appended claims.

I claim: 1. An alternating current circuit comprising a source of alternating current, means connected to said source, said means including a device having inherent rectifying action, and choke-resistor network means for substantially excluding rectifled current from said source of alternating current.

2. An alternating current circuit comprising a source of alternating current, a load connected to said source, said load including a device having inherent rectifying action, and low direct current resistance choke means across said device for substantially excluding rectified current from said source of alternating current.

.3. An alternating current circuit comprising a source of alternating current, a load connected to said source, said load including a device having inherent rectifying action, and choke-resistor network means in said circuit for substantially excluding rectified current from said source of alternating current.

4. An alternating current circuit comprising a source of alternating current including a transformer having a core and a primary winding and secondary winding on said core, means connected to said secondary winding, said means including device having inherent rectifying action, and a choke-resistor network including a high impedance-low direct current resistance choke connected across said load to substantially preclude flow of direct current through said secondary winding and enhance the magnitude of direct current through said load.

5. An alternating current circuit comprising a source of alternating current including a transformer having a core and a primary winding and secondary winding on said core, a load connected to said secondary winding, said load including a device having inherent rectifying action, and choke means including a high impedance-low direct current resistance choke connected across said load to substantially preclude flow of direct current through said secondary winding and enhance the magnitude of direct current through said load.

6. An alternating current circuit comprising a. source of alternating current including a trans former having a core and a primary winding and secondary winding on said core, a load connected to said secondary winding, said load including a device having inherent rectifying action, and a choke-resistor network including a high impedance-low direct current resistance choke connected across said load and a relatively'high resistance in the connection from said transformer secondary winding, to substantially preclude flow of direct current through said secondary winding and enhance the magnitude of direct current through said load.

'7. An alternating current arc welding circuit comprising a source of alternating current, a load connected to said source, said load including a pair of electrodes, one of which constitutes a welding electrode, and choke-resistor network means between said source of alternating current and said load.

8. An alternating current arc welding circuit comprising a source of alternating current, a load connected to said source, said load including a pairof electrodes, one of which constitutes a welding electrode and the other the work, and choke means of low direct current resistance connected across the circuit intermediate said source and said pair of electrodes.

9. Am alternating current arc welding circuit comprising a source of alternating current including a transformer having a core and a primary winding and secondary winding on said core, a load connected to said secondary winding, said load including a pair of electrodes, one of which constitutes a welding electrode, a high impedance-low direct current resistance choke connected across the circuit intermediate said transformer and said load, said choke including a core, a low resistance primary winding and a secondary winding on said core, and means tuning said secondary winding to substantially the frequency of said source of alternating current.

10. An alternating current arc welding circuit comprising a source of alternating current in- 6 a core, and a relatively high resistance in the connection from said transformer secondary winding.

DEAN C. GIRARD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,310,015 Agnew Feb. 2, 1943 2,322,709 Owen June 22, 1943 

